Qualitative fit testers (QLFT) may be used to test the integrity of a gas mask and the fit of the mask to a specific individual. Such testers are “qualitative” in the sense that they do not quantify the size of a leak, but merely that the leak is present. Generally, the mask is fitted on the individual and an aerosol of a solution having a distinct flavor is caused to flow against the mask and the fitted seal between the mask and the individual. If the individual can taste the distinct flavor of the solution with the mask on, the mask is known to leak, likely around the fitted seal. Adjustments are made and the test repeated until the individual can no longer detect the aerosol solution.
Qualitative fit testing requires the participation of the individual being fitted. The sensitivity of individuals to a particular testing solution may vary. Accordingly, the fit testing is often preceded by a threshold test to assess the sensitivity of the individual to the flavored aerosol solution so that a proper dose can be determined for the fit test. The threshold test is usually conducted without a mask on the individual. Because of the absence of a mask during the threshold test, the aerosol solution for the threshold test is often a diluted version of the aerosol solution used in the fit test.
The United States Department of Labor, or more specifically the Occupational Safety and Health Administration (OSHA), has promulgated accepted fit testing protocols for qualitative fit testing, codified at 29 CFR 1910.134 (hereinafter “OSHA standards”), which is incorporated by reference herein except for express definitions that may be included therein. The OSHA standards include guidelines for the use of aerosol solutions containing saccharin or Bitrex® (BITREX). Saccharin is an artificial sweetener comprising benzoic sulfinide. BITREX is a bittering agent comprising denatonium benzoate, the name being a registered trademark of Johnson Matthey Public Limited Co., United Kingdom. The OSHA standards also include guidelines for mixing aerosol solutions for threshold testing and fit testing.
Current hand-held QLFT aerosol generators utilize a squeeze ball pressure generator operatively coupled with a nebulizer to deliver aerosols during a qualitative fit test. The squeeze ball is actuated manually by testing personnel. A single qualitative fit test may require in excess of 250 actuations of the squeeze ball pressure generator. Testing personnel may test several individuals in a single day, requiring actuation of the squeeze ball pressure generator thousands of times in the course of a full day of qualitative fit testing.
The squeeze ball pressure generator is known to produce concentrations and size distributions that vary substantially. Chan et al. documents the output characteristics of the DEVILBISS 40, a nebulizer that has been widely used for QLFT applications. See Chan, K. N., M. M. Clay and M. Silverman, “Output Characteristics of DeVilbiss No. 40 Hand Held jet Nebulizers,” Eur Respir J, 1990, 3, 1197-1201, which is hereby incorporated by reference except for definitions explicitly defined therein. Chan reports a variation in mass concentration from 14.3-mg to 30.7-mg saline and variation in the median diameter of aerosol droplets from about 6- to 12-micrometers (μm). The variations can stem from non-repeatability of generated actuation pressures, particularly between different test operators. Assuming median levels midway between the minimum and maximum concentrations/aerosol droplet sizes (i.e. 22.5-mg concentration and 9 μm aerosol droplet size), the non-repeatability from median is about ±36% for the concentration and ±3-μm for the aerosol droplet size.
The FT-13, distributed by 3M, Minnesota, USA, is a standard QLFT nebulizer on the market intended to be an equivalent of the DEVILBISS 40. The FT-13 includes a reservoir for holding about 5 cubic centimeters (cc) of aerosol solution. The size of the reservoir requires refilling the reservoir after a limited number of qualitative fit tests. Moreover, the orientation of many current hand-held QLFT aerosol generators must be maintained in a substantially vertical orientation when aerosol solution is in the reservoir, lest the aerosol solution be spilled out of the nebulizer. Existing nebulizers are also prone to clogging when certain aerosol solutions, such as saccharin, are utilized.
Testing personnel must also keep track of the number of squeezes during the entirety of the test in order to comply with the OSHA standard. Test results are typically manually written after each qualitative fit test.
Given the inconveniences and variations associated with present fit testing apparatuses and procedures, an improved system that substantively complies with OSHA-accepted fit testing protocol is welcome.